What "holdup?. The date given was that devices would be updated by the end of September, which is still more than 5 weeks away.

Unless October starts and the update still isn't available, there is no delay/holdup...

I thought end of september was for the lower end devices. I thought 92x would get it first. But I mean, it's not a big deal, just the fact that VERIZON of all people would push the update on day 1, they've been outspoken about their dislike for windows phone before. And ATT, the "premier partner" is still testing

The release of GDR2 for the HTC 8X doesn't really have much to do with the Lumia 920 rollout. The Lumia 920 is receiving a much more significant software update because Nokia is packaging some software and firmware improvements with Microsoft's GDR2 update.

That said, AT&T is holding up the update at this point. American carriers are notorious for taking their time with pushing updates, and frequently opting to simply not deliver them.

The release of GDR2 for the HTC 8X doesn't really have much to do with the Lumia 920 rollout. The Lumia 920 is receiving a much more significant software update because Nokia is packaging some software and firmware improvements with Microsoft's GDR2 update.

That said, AT&T is holding up the update at this point. American carriers are notorious for taking their time with pushing updates, and frequently opting to simply not deliver them.

Its not like there is much more to test. The Lumia 1020 has GDR2+Amber pre-installed. the hardware is identical except for the screen, one gig more memory and the camera.

I really wish I had gone with Nokia than the 8X but at the time the nokia devices didn't seem very appealing over the 8x. I'd rather update my device manually than wait for a carrier that may or may not ever push the update even if it does risk my device bricking.

T-Mobile approved the 520 but at&t hasn't approved the 521.
T-Mobile approved the 810 but at&t hasn't approved the 820.
Verizon approved the 928 but at&t hasn't approved the 920.

Different carriers were able to get similar phones tested and approved but AT&T can't?

The odd thing about that, beyond the fact that you mixed up the 520 (AT&T) and 521 (T-Mobile) is that AT&T has been shipping the 520 with GDR2/Amber for at least a couple of weeks now, and all AT&T 520 customers should have the update (and well before the T-Mobile 521 users got the upgrade). I'm not sure why that chart claims that AT&T hasn't approved it.